The 22-year-old becomes Jose Mourinho's first signing since being appointed the club's new manager at the end of last month.
Bailly, who has arrived at Old Trafford on an inital four-year contract, described the move as "a dream come true", while Mourinho hailed him as a defender with "great natural talent" who has the potential to become one of the world's best.
However, the question on the lips of many will be a simple one: who is Eric Bailly?
So, who is Eric Bailly?
Bailly initially caught the eye of scouts while appearing in a youth tournament in Burkina Faso. Espanyol snapped up the strapping young defender in 2011, when he was aged just 17. However, due to work permit issues, it was another 10 months before he would be able to represent the club.
He made his debut for the senior side in October 2014 – a 2-0 win over Real Sociedad. He made only a further four appearances before being called up to the Ivory Coast squad for the 2015 Africa Cup of Nations. Les Éléphants went on to win the tournament with a penalty shoot-out victory over Ghana in the final. Bailly, who started all six of their games at the tournament, converted his spot-kick.
Bailly signed for Villarreal during the tournament and replaced Gabriel, who had recently joined Arsenal. He has established himself as one of the club’s first-choice centre-halves in the time since, combining well with Victor Ruiz, and was key in El Submarino Amarillo earning a top-four La Liga finish this term.
Haven’t I seen him before?
Yes, you may have spotted him a couple of months ago, impressing in his side’s Europa League semi-final first leg victory over Liverpool.
Although Jurgen Klopp’s side had the better of the game, Bailly kept them at bay and was excellent until he went off injured in the second half.
The thigh strain he sustained kept him out of the return leg, which Liverpool won at a canter. Could it have been a different story with Bailly on the pitch?
Why should United sign him?
At 6ft1in and with an imposing style, Bailly should meet the physical demands of the Premier League.
The Ivory Coast international was part of a defence which conceded just 35 goals in 38 games and played all the way across it, deputising in the full-back positions when necessary.
Most importantly, though, he would provide Chris Smalling with a bonafide partner in the centre of defence, despite Daley Blind’s admirable efforts over the past nine months.
Bailly is considered to be a little raw and unpredictable.
Like any young defender, he has a mistake in his locker and there is a sense that United would be investing in potential rather than a finished product.
The prices being quoted – £30m in some quarters – will seem steep to some and a snip to others. Ultimately, it will depend on whether Bailly fulfils his promise.
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